You really need to measure the width of your opening left in your cabinets for the DW. The US standard is 24". Your opening could end up wider. Thus, people generally get a panel that is 24" minus 1/4" or so for clearance (about an 1/8" gap on either side). If you follow the template minimums you will end up with a gap that is too large around the DW panel.

We're putting the DW on the end of a row of base cabinets, with a cover panel and fridge on the other side. So I guess we just cut it however we want? We need to order doors well in advance of base cabinet construction.

You really need to measure the width of your opening left in your cabinets for the DW.

We did the opposite. We ordered the 23-5/8" panel and then made sure everything around it fit correctly - so it goes refrigerator - T shaped panel to support counter over dishwasher - dishwasher (with 1/8" clearance on each side of the door) - 6" cabinet - sink - trash - cooktop - condiment pullout - filler. The filler was "customized" to fit the remaining space.

Note the panel to hold up the counter over the dishwasher. You need that too - the dishwasher itself can't support a stone counter.

We were going to use L brackets mounted to the back wall and the fridge cover panel to hold up the counter. So we have, from L to R:

Fridge, floor-to-ceiling cover panel, DW, sink cabinet, cab...

I'm not able to picture the "t-shaped panel" you used... where does it go? Sounds like you have a similar layout.

I don't have a good picture with me, but I'll post one later. The fridge is encased in paneling and has a 3" "frame" all the way around (left, top and right). Next to the fridge but counter-height, there is a 3/4" panel, which "turns the corner" so from front of cabinets to wall, the panel is 3/4", but the front is 1-1/2" (I guess it looks like a filler from the front).

Ah, I think I got it from your description. Thank you!